1. Field of the Invention
The present invention relates to a control system for a continuous vulcanization line for rubber materials, such as unvulcanized sponge rubber materials including foaming agents, and specifically to an automatic control system which optimally controls the output power of microwave generated by a microwave vulcanizer employed in a continuous vulcanization line utilized for manufacturing an extrusion-molded sponge rubber product suitable for weatherstrips, for example an automotive weatherstrip provided between a vehicular body and a door.
2. Description of the Prior Disclosure
Recently, there have been proposed and developed various continuous vulcanization lines for heating and foaming unvulcanized rubber materials, such as natural rubber, ethylene propylene rubber or the like. In general, the continuous vulcanization line comprises an extruder for pre-forming a sponge rubber material by way of extrusion molding or pressing, a primary heating system including a hot-air vulcanizer for externally heating the pre-formed sponge rubber material and a microwave vulcanizer for internally heating the pre-formed sponge rubber material so as to pre-foam and pre-vulcanize the pre-formed rubber material, a secondary heating system, such as a hot-air vulcanizer or a hot-press vulcanizer for finally heating the pre-foamed rubber material, a cooling pool for cooling the finally vulcanized and foamed rubber material, and a plurality of roller conveyors provided in the manufacturing line, for conveying the sponge rubber product.
In such a conventional continuous vulcanization line for rubber materials, a desired outside dimension of the extrusion-molded and foamed sponge rubber product is manually adjusted so that the operator measures the outside dimension of the final product through a profile projector and manually changes the operating condition of the manufacturing line when the measured dimension does not satisfy a predetermined criterion based on an acceptable outside dimension of the extrusion-molded rubber product.
In another conventional continuous vulcanization line for manufacturing an extrusion-molded rubber hose having a simple, annular shape, an optical measuring device is provided for monitoring the change in an outside dimension of the rubber product, so as to automatically control a rotational speed of an extruding screw employed in an extruder and a rotational speed of a motor employed in a roller-conveyor. The extruding speed is varied depending on a vulcanizing speed of the rubber material. One such conventional continuous vulcanization line having a controller automatically controlling both an extruding speed and a final rubber product conveying speed, has been disclosed in Japanese Patent Second Publication (Tokko) Showa 56-5178.
In the former prior art, the manual adjustment of operating condition is troublesome. In addition, a considerably skilled operator is required for quickly and precisely adjusting the operating condition of the manufacturing line.
In the latter prior art, supposing that the rubber product has an extremely deformed, complicated cross-section, there is a possibility that the rubber product is locally deformed depending on both change in extruding speed and change in tension based on a roller-speed change of the roller conveyor, during operation of the controller which varies both speeds, namely the extruding speed and the conveying speed when the outside dimension measured by the optical measuring device does not satisfy the criterion.